Sir Keir Starmer accused Tories of “undermining the union” and treating Scotland with “utter disdain” by refusing to oust Boris Johnson.
The Labour chief slammed leading Conservatives during Prime Minister’s Questions for propping up the Tory leader after it was confirmed he is being investigated by police for lockdown breaches.
Sir Keir said government ministers had shown a lack of respect for their Holyrood colleagues after Douglas Ross was branded a “lightweight” when he turned against the PM.
The opposition leader said Mr Johnson’s underlings were becoming more “complicit” in his actions while they refuse to remove him.
The Labour MP said: “The reality is we now have the shameful spectacle of a Prime Minister of the United Kingdom being sucked into a police investigation, unable to leave the country, incapable of doing the right thing, and every day the Cabinet fail to do the right thing they become more complicit.”
The exchanges took place as MPs were braced for the release of Sue Gray’s inquiry into Westminster parties held while the nation was in lockdown due to Covid.
Earlier this week it emerged a birthday party was hosted in Downing Street for Mr Johnson in June 2020 while indoor mixing restrictions remained in place.
But the Prime Minister refused to be drawn on whether he lied to Parliament as he was grilled by Sir Keir – instead saying he would wait for the probe findings to come out.
SNP Westminster leader Ian Blackford also lambasted Mr Johnson and said the Met Police investigation into his government was “unprecedented”.
The SNP Westminster chief said the PM “partied while the public suffered” as he read out his “rap sheet” and urged him to step down.
He said: “We have a Prime Minister who is being investigated by the police for breaking his own laws. Absolutely unprecedented.”
Mr Johnson appeared to respond with a jibe about Mr Blackford’s weight.
The Prime Minister was also asked by Labour boss Sir Keir whether he would publish Sue Gray’s report in full.
It comes after fears the government would try to hold back any damaging finds to boost the Tory leader’s fortunes.
Mr Johnson had said previously all of the inquiry report would go out and said today: “I will do exactly what I said.”
A Scottish Tories spokesperson said: “Under Douglas Ross’ leadership, the Scottish Conservatives won 100,000 more votes than ever before in last year’s elections.”